1. Field of the Invention
The present invention relates to a vehicle surroundings monitoring apparatus and method which detects an object existing in the surroundings of a vehicle from images obtained by a plurality of image sensors such as cameras mounted on the vehicle, and more particularly to a program for use in causing a computer to perform processing of the apparatus.
2. Description of the Related Art
In recent years, there is known a technology of imaging the surroundings of a vehicle with a plurality of image sensors such as CCD cameras mounted on the vehicle, detecting a distance between an object such as a pedestrian existing around the vehicle and the vehicle based on a difference (parallax) between images obtained by a plurality of image sensors, determining an object such as a pedestrian at high risk of collision on the basis of the detected result, and presenting information to a driver (for example, refer to Japanese Patent Laid-Open No. 2001-6096 (hereinafter, referred to as Patent Document 1).
In the vehicle surroundings monitoring apparatus disclosed in Patent Document 1, a stereoscopic camera composed of two infrared cameras is mounted on a vehicle with an image obtained by a right camera (right image) of the stereoscopic camera used as a standard image. The vehicle surroundings monitoring apparatus binarizes the standard image by setting a value of “1” (white) if the luminance of an area is a predetermined threshold value or higher and setting “0” (black) otherwise, labels the binary image, and extracts objects existing around the vehicle. Then, the vehicle surroundings monitoring apparatus searches the image (left image) obtained by the left camera for an object corresponding to each of the objects extracted from the standard image and detects the position of the object with respect to the vehicle on the basis of the parallax between the object in the standard image and the object corresponding to the object in the left image.
In the surroundings of the vehicle, however, there may be objects (background objects) other than pedestrians or other objects as targets of detection (detection objects) such as, for example, buildings, or fences. If the surroundings are imaged by the image sensors mounted on the vehicle in this situation, the background objects are imaged as a scene together with the detection objects. Therefore, when the objects are extracted after the binarization of the obtained image, also areas corresponding to the background objects are extracted in addition to areas corresponding to the detection objects.
Moreover, if the detection object and the background object are located on a straight line, for example, viewed from the right camera in the vehicle surroundings monitoring apparatus in Patent Document 1, the detection object and the background object are extracted with the both objects overlapped with each other in the standard image. Therefore, an area corresponding to the detection object cannot be separated from an area corresponding to the background object in the standard image, by which the objects cannot be properly extracted. Accordingly, in this situation, there has been a problem that the position of an object with respect to the vehicle cannot be properly detected since the object corresponding to the extracted object cannot be found or the parallax cannot be obtained correctly.